Tow-crimping apparatus

ABSTRACT

A tow-crimping apparatus that includes a pair of crimper rolls associated with a crimper chamber and guides on each side of the rolls to control the path of the tow advancing from the nip of the rolls to the chamber wherein the improvement comprises forming the guides from graphite to increase wear life of the guides without causing wear to the rolls or staining of the tow.

United States Patent Inventor Oscar La Rue Price Kinston, N.C. Appl. No. 21,971 Filed Mar. 23, 1970 Patented Jan. 11, 1972 Assignee E. I. du Pont de Nemours and Company Wilmington, Del.

TOW-CRIMPING APPARATUS 1 Claim, 4 Drawing Figs.

US. Cl... 28/1.6 Int. Cl D02g 1/] Field of Search 28/1.6, 1.7, 72.14;252/l2;l88/251;23/209.1

[56] References Cited UNITED STATES PATENTS 2,035,988 3/1936 Seabury et al. 252/12 3,160,941 12/1964 Williamson 28/1 .6

Primary Examiner- Louis K. Rimrodt Attorney-Howard P. West, Jr.

ABSTRACT: A tow-crimping apparatus that includes a pair of crimper rolls associated with a crimper chamber and guides on each side of the rolls to control the path of the tow advancing from the nip of the rolls to the chamber wherein the improvement comprises forming the guides from graphite to increase wear life of the guides without causing wear to the rolls or staining of the tow.

INVENTOR OSCAR LORUE PRICE ATTORNEY TOW-CRIMPING APPARATUS BACKGROUND OF THE INVENTION This invention relates to an apparatus for crimping synthetic filamentary tow and more particularly to a novel crimper disc associated with the crimping apparatus for controlling the path of the tow.

Stuifer box crimpers of many design variations have been disclosed in the patent art. One such crimper is that described by Hitt in U.S. Pat. No. 2,311,174, dated Feb. 16, 1943, who also recognized the desirability of installing crimper disc at each side of and below the line of contact of the two crimping rolls to control the path of tow from the nip of the rolls into the stuffer box. To prevent entanglement of filaments between the ends of the crimper rolls and the crimper discs, it is necessary that a firm, rubbing contact between the ends of the rolls and the disc be maintained. The use of crimper discs comprising a relatively hard material, such as a ceramic, results in an unacceptable rate of wear on the edges of the crimper rolls whereas the use of a relatively soft material disc, such as phosphor bronze, entails frequent interruptions of the process to replace discs worn by the abrasive action of compressed filamentary tow passing over their surface. Also, attempts to employ solid synthetic polymeric crimper discs of generally accepted lubricous and abrasion resistant characteristics have not been entirely successful because of the poor thermal conductivity of such discs which result in the fusion of filaments near the edges of the crimped tow.

The problem of disc wear has long been recognized and several solutions proposed. McGill, for example, in U.S. Pat. No. 3,] 13,367, issued Dec. 20, 2963, proposed to improve the life of nylon inserts for holding tow in the nip of a pair of crimping rolls by using a shape which prevented rotation of the insert. McGills arrangement insured that the grooves worn in the insert remained aligned with the moving tow so that snagging was minimized. An improvement was obtained in useful life but continued wear was recognized. Dennis proposed in U.S. Pat. No. 3,237,270 issued Mar. 1, 1966, that crimper discs be composite structures with the central portion being a hard material such as cast iron and the outer portion being a soft material such as bronze. Dennis also obtained an improvement in performance, but disc wear was still a recognized problem.

A different type of solution to the problem of disc wear was proposed by Coffin & Saxon in U.S. Pat. No. 3,353,233, issued Nov. 21, 1967, wherein movable ribbon side plates are substituted for crimper discs. By advancing the ribbon from time to time, a new surface is substituted for the section of worn ribbon surface abraded by the tow. The apparatus required for this arrangement is considered to be relatively complicated. A different approach is also presented by Knowlton in U.S. Pat. No. 3,399,439 issued Sept. 3, 1968, wherein a particularly abrasive fiber being passed through a stuffer box crimper is blended with a nonabrasive fiber to prevent undue wear on crimper parts. The crimped product, of course, is of necessity a mixture of two different fibers, which is not always desirable.

SUMMARY OF THE INVENTION The present invention provides a novel crimper disc which has low abrasiveness with respect to the ends of the crimper rolls combined with a high resistance to the abrasive action of compressed filamentary tow. Furthermore, the invention provides improved crimper performance without any adverse effect upon the crimped tow, such as staining or snagging of filaments.

The crimper disc of the invention also contributes to ease of machine maintenance. After a long period of use, the disc is easily and rapidly resurfaced by hand or machine lapping.

In accordance with the present invention, there is provided a stuffer box crimper disc composed of graphite.

Surprisingly, it has been found that the use of a crimper disc composed of graphite in a normal stuffer box crimper results in a multiple increase in wear life of the disc and of the crimper rolls without any significant staining of the filaments passing through the crimper. The absence of staining is entirely unexpected for this use of graphite.

Crimper discs suitable for the present purpose may be cut from high purity extruded or molded synthetic graphite rod which is commercially available from several manufacturers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side elevation view of a stuffer box crimper, partially in cross section, showing the location of the crimper disc.

FIG. 2 is a front elevation of FIG. I.

FIGS. 3 and 4 are side and top views, respectively, of the crimper disc.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the Figures, in operating the crimper tow is forcibly packed into crimper chamber 2 by crimper rolls 1 which are driven by a mechanism not shown. One of the crimper rolls 1 is mounted for movement toward and away from the other as indicated in FIG. 1 to permit controlled loading of the tow at the nip of cooperating rolls 1. The bottom of crimping chamber 2 is closed by clapper 3 which pivots about shaft 4 and is under a controlled degree of loading schematically represented by cantilevered weight 5. When sufficient pressure has developed in crimper chamber 2 to overcome the closing force on clapper 3, it is forced open by the emerging tow. Control of the path of the tow at the entrance to crimping chamber 2 is maintained by crimper discs 6 which are urged into contact with crimper chamber walls 7 and rolls 1 by a mechanism schematically represented by screws 8 and springs 9. Crimper discs 6 are composed of graphite.

It is preferred to employ a circular crimper disc because of the convenience in fabrication as well as orientation relative to the crimper roll. However, other shapes may also be used and are within the contemplation of this invention.

In a typical crimper installation, a flat circular crimper disc having a diameter of about 2.5 inches (6.35 cms.) and a thickness of about 0.3-0.5 inch (0.76l.27 cms.) is used. The discs are cut from high-purity synthetic graphite rods, such as UCAR grade AGSX sold by the Union Carbide Corporation or graphite grade GSP sold by the Carborundom Company. A typical graphite rod has a bulk density of about 1.67 grams per cm., a grain size of 0.0l60.60 inch (0.04] .5 cms.), a flexural strength with the grain of about 31 pounds per square inch (2.2 kg./cm. and an ash content of about 0.13 percent. Flat surfaces of the disc are easily machineor hand-lapped to remove tool marks and achieve required flatness.

In one 29 hour test of the invention a 450,000 denier tow composed of 2.25 denier semidull polyethylene terephthalate filaments containing 0.3 percent TiO is crimped by passing through a stuffer box crimper having graphite discs as described above. Careful inspection of the crimped tow reveals no staining. The discs show very minor wear, and the crimper rolls show no signs of wear.

The present invention provides an easily fabricated and easily installed crimper disc which is effectual in the reduction of wear rate by synthetic filamentary tow. In a give installation, the wear life of a graphite crimper disc may be as high as 65 operating hours in comparison with an average life of l-6 hours for a bronze crimper disc and an average life of 3-10 hours for a bronze disc having a cast iron center. Furthermore, in addition to the longer life of the disc itself, the graphite disc causes no detectable wear of the crimper rolls moving in contact with the disc.

What is claimed is:

I. In an apparatus for crimping synthetic filamentary tow including a pair of crimper rolls cooperating to form a nip between the rolls through which tow passes to a crimper chamber associated with said rolls, said crimper chamber havfrom 0.016 to 0.60 inch and a flexural strength with the grain of about 3! pounds per square inch, said graphite discs contacting said tow without staining it as it passes through said apparatus.

23 g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,633, 55 Dated January 972 Inventor-(s) Oscar LaRue .Price It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, colum 3, line "4, after "said",

first occurrence, insert nip to said Signed and sealed this 30th day of May 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,J'E. ROBERT GOT'ISCHALK Attesting Officer Cormissioner of Patents 

1. In an apparatus for crimping synthetic filamentary tow including a pair of crimper rolls cooperating to form a nip between the rolls through which tow passes to a crimper chamber associated with said rolls, said crimper chamber having an entrance adjacent said nip, and crimper discs positioned on each side of said rolls below said nip, said discs engaging said rolls and said chamber to control the path of said tow from said chamber, the improvement comprising: said crimper discs consisting essentially of graphite having a bulk density of about 1.67 grams per centimeter, a grain size of from 0.016 to 0.60 inch and a flexural strength with the grain of about 31 pounds per square inch, said graphite discs contacting said tow without staining it as it passes through said apparatus. 